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The agreement of IOP measurements between Corvis® ST, Goldmann applanation tonometry (GAT), Tonopen Avia®, Icare® and ocular response analyzer (ORA)®

Poster Details

First Author: W.Halim MALAYSIA

Co Author(s):    M. Rana   S. Naroo   M. Nessim   S. Shah     

Abstract Details


To study the agreement of IOP measurements by Corvis® ST (Oculus Inc) with Goldmann applanation Tonometry (GAT), Tonopen Avia® (Reichert Technologies) , Icare® (Icare Finland Oy) and Ocular Response Analyzer®(ORA) by Reichert Technologies).


The outpatient clinic of the Birmingham and Midland Eye Centre, United Kingdom.


This is a single blinded cross sectional study that involved 136 eyes from 73 glaucoma patients. All patients underwent IOP measurements by GAT (IOPgat), Tonopen Avia (IOPtono), Icare (IOPi), ORA (IOPg and IOPcc) and Corvis ST (IOPcst) . The tonometry with all the tonometers except GAT was randomised and performed by a single operator. The GAT was performed at the end of examination by a different operator. The agreement of the IOP measurements were analysed by intraclass correlation coefficient (ICC) and Bland Altman plot. The outcome measures were set at 95% limits of agreement for IOP measurements between the different tonometers.


Mean IOP for all examined eyes was 14.25 ±3.4 for IOPcst, 15.5 ±4.3 mmHg for IOPgat, 13.09 ±4.8 mmHg for IOPi , 14.4ḟ3.7 mmHg for IOPtono, 12.7±5.5 for IOPcc and 14.98±5.2 for IOPg. There was no statistically significant difference in IOP measurement among different tonometers except between the IOPi which is significantly lower than IOPgat and IOPtono. Correlation analysis showed a moderate to high correlation between all the devices ( P<0.01) except for IOPcc. The IOPcst have the high correlation with the IOPgat, IOPi, IOPtono, and IOPg (p<0.01).The Bland-Altman analysis revealed the highest bias with IOPcc ( -8.6 to +7.1) with 95% limits of agreement among the tonometers.


The correlation and limit of agreement among the tonometers are variable. In this study, the IOPg and IOPcst has significantly high correlation among the tonometers.The Corvis ST is a reliable alternative for tonometry. However, the IOP measurements taken with each device may not be interchangeable.

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